Furnace pipe insulation and method



Feb. 2, 1965 J. R. BROUGH FURNACE PIPE INSULATION AND METHOD 3Sheets-Sheet 1 Filed May 2, 1962 0 R wv/w mm mm m 7 h T m Feb. 2, 1965J. R. BROUGH FURNACE PIPE INSULATION AND METHOD 3 Sheets-Sheet 2 FiledMay 2, 1962 INVENTOR.

Afzamzys.

Feb. 2, 1965 J. R. BROUGH FURNACE PIPE INSULATION AND METHOD 5Sheets-Sheet 3 Filed May 2, 1962 United States Patent 3,168,297 FURNACEPEPE ENSULATION AND METHQD John R. Brought, Gary, Ind, assignor toInland Steel (Iompany, Chicago, llL, a corporation of Delaware Filed May2, 1962, Ser. No. 193,575 22 Claims. (Cl. 263-6) This invention relatesin general to furnaces and more particularly to an insulated pipeconstruction for use in high temperature furnaces. It dealsspecific-ally with an improved insulation construction and method ofinsulating water cooled furnace pipes.

This application is a continuation-in-part application of the copendingapplication entitled Insulation, filed June 3, 1961, bearing Serial'No.121,427, now abandoned.

It is a conventional practice in the iron and steel industry to providereheating furnaces for bringing billets of steel up to requiredtemperature in preparation for rolling operations. One well known typeof furnace utilized is described as an underfired furnace. In theoperation of such a furnace, fuel is burned in the lower regions of thefurnace while billets of steel pass over the burning fuel and are.heated thereby to a predetermined temperature. The fuel might be naturalgas, coke oven gas, or oil, or the like. it is not unusual fortemperatures in the neighborhood of 2400 F. to be generated in such afurnace when a finished billet temperature of in the neighborhood of2100" F. is sought for a rolling operation, for example.

In passing through a furnace while undergoing reheating to apredetermined temperature, the billets are conventionally supported onlongitudinally extending skid means or tracks upon which thetransversely extending billets slide. With billets of relatively smallsize, these tracks or skid means might be solid rails but for heavierbillets and, for that matter, for all high temperature end dischargefurnaces, water cooled skid means in the form of skid pipes are standardequipment.

These water cooled skid pipes normally have a wear strip welded on theirupper surface and extending longitudinally of the pipes to support thebillets in sliding relationship. In the underfired' reheating furnace,for example, the longitudinally extending horizontal skid pipes arecarried by transversely extending horizontal crossover pipes which inturn are supported by vertically extending support pipes. Waterpreferably courses through all the pipes in a well known manner toprovide cooling thereof.

In recent years the use of insulation on such Water cooled pipes hasbecome popular because of the considerable water heat losses sufferedwhen non-ii isulated water cooled pipes are utilized. With non-insulatedwater cooled, skid pipesin use. in an underfired furnace, for example,it would not be unusual for up to 25% of the input of natural gas, forexample, to be. lost in heating the water rather than the steel billets.This, in turn, effects the furnace capacity, in many cases, since afurnace normally has a limited fan, stack, or burner capacity and onlyso much fuel can be pumped through it. in addition, where the ski pipesare not insulated, uneven heating of the billets frequently results andin some cases it is serious enough to prevent rolling thereof.

A number. of means for insulating Water cooled high temperature furnacepipes have been utilized in the past. For example, the Schmidt UnitedStates Patent No. 2,482,878, entitled Reinforced Refractory PipeInsulation, discloses an insulation construction of the general type nowin use in the iron and steel industry. Each of the insulationarrangements heretofore utilized has serious drawbacks, however. In theinsulation construction disclosed in the Bloom United States Patent No.2,693,352,

there is a tendency for the refractory material to flakeaway from thereinforcing reticulated metal structure exposing it to the heat of thefurnace which not only considerably reduces the effectiveness of theinsulation but materially shortens its life. refractory is caused by amarked temperature. diiference between the refractory material within oraround the reinforcing metal structure and the overlying refractorymaterial. a

It is an object of this invention to provide a new andimprovedinsulation construction.

it is another object to provide a-neW and improved insulationconstruction forwater-cooled high temperature furnace pipes.

It is still another object toprovide a new and improved insulationconstruction for'water cooled skid pipes, crossover pipes, and verticalsupport pipes inan underfired steel mill reheating furnace.

It is a further object to provide an insulation construc tion for watercooled high temperature furnace pipes which is highly durable.

It is yet a further object to provide an insulation construction forwater cooled hightemperature furnace pipes which is substantially easierto apply and less expensive than insulations heretofore utilized.

It is still another object to provide a reinforced insulationconstruction for water cooled high temperature furnace pipes whichrequires a minimum of high cost, heat resisting, reinforcing material.

It is another object to provide an insulation constructi-on wherein thereinforced means incorporated therein does not set up lines or planes ofweakness. in the insulas tion.

It is still another object to-provide an improved in-. sulated furnacepipe.

It is another object to provide a new andimproved method forinsulatingfurnace pipes.

It is a further object to provide a method for insulating water cooledhigh temperature furnace pipes which. is simpler and less expensive andproduces. results superior to those methods heretofore utilized.

It is a further object to provide a method for applying insulation towatercooled high temperature-furnace pipes which incorporates means forfacilitating relatively in, creased support for the refractoryinsulation. utilized, while it remains in its plastic state.

The above and other objects are realized inaccordance with the presentinvention by providing a new and'im, proved insulation construction forWater cooled; high tem perature furnace pipes and? a method: forapplying this insulation. Briefly, the invention contemplates encirclinga conventional steel furnace pipe havinga water carrying capacity withcoils of wire: and securing the coils .tothe pipe with tie-wiresthreaded through the coils- The coils are defined by wires, in.themselves. coiling'about axes encircling the pipe. Refractory materialin a plastic state is applied to the pipe so that it. is in. intimatecontact with the coils. 'andthe outer surface of the pipe.

One, aspect of the present invention lies in the utiliza tion ofalternating orotherwise successively arrangedindividual' encirclingcoils of high temperature heat resisting alloy wire and ordinarycarbonsteel wire. In such case, the coils are secured to the pipe by tiewiresof corresponding composition threaded through the coils.- Sincethese alternating or otherwise successively arranged coils of carbonsteel Wire and high-temperature heat resistant alloy wire are spaced in,relatively close proximity of one another the refractory material issupported while in its plastic state without the use of a form. Afterthe refractory is hardened by firing, however, substantially lesssupport isneeded to. retain it on the pipe. and, there- T'hi-s flakingoff of the fore, the coils of high temperature heat resistant alloy wireare sufiicient alone to effectively support the refractory wire; Theordinary carbon steel wire, due to its inherent physical characteristicsand the high furnace temperatures, tends to lose its strength. Byutilizing this arrangement of high temperature heat resisting alloy wirecoils and carbon steel Wire coils, the number of alloy wire coilsrequired is substantially reduced without seriously diminishing the lifeor effectiveness of the finished insulation.

Another aspect of the present invention lies in the utilization of asubstantially continuous coil of high temperature heat resisting alloywire Wound spirally of the furnace pipe in parallel realtionship with asubstantially continuous spirally wound coil or coils of ordinary carbonsteel wire. In such case, of course, tie wires of correspondingcomposition are threaded through the spirally Wound coils and the coilsmight be alternated, or otherwise successively arranged in a generallysimilar fashion.

Another aspect of the present invention lies in the utilization ofrelative larger 7 diameter ordinary carbon steel wirecoils andrelatively lesser diameter high temperature heat resistant alloy Wirecoils. This arrangement of the wire coils is such that anirregularstress pattern is set up in the hardened refractory insulation tovirtually eliminate serious lines or plane of weakness in theinsulation.

The invention, both as to its organization and method of operation,taken with further objects and advantages thereof, will best beunderstood by reference to the following description taken in connectionwith the accompanying drawings, in which: 7

FIGURE 1 is a perspective view of conventionally arranged water cooledfurnace pipes in an underfired steel mill reheating furnace;

FIGURE 2 is a front elevational View of a portion of support pipe or across-over pipe showing one form'of an arrangement of reinforcing wirecoils prior to the application of refractory material;

FIGURE 3 is a rear elevational view of the arrangement shown in FIGURE2;

FIGURE 4 is a view similar to FIGURE 3 showing the refractory insulatingmaterial applied to a portion of the pipe;

' FIGURE 5 is a top plan view of the reinforcing wire coil arrangementfor a skid pipe, prior to the application of refractory material;

FIGURE 6 is a front elevational view of the pipe shown in FIGURE 5; x

FIGURE 7 is a'view similar to FIGURE 5 showing the refractory materialapplied to a portion of the pipe;

FIGURE 8 is a front elevational view of a portion of a support pipe or across-over pipe showing another form of an arrangement of reinforcingwire coils prior to the application of refractory material;

furnace, for example, is shown generally at 10. The description of theuse of an insulation construction and the method of constructing it,embodying the features of this invention, as applied to furnace pipesutilized in an underfired furnace, is exemplary only, as will readily beunderstood and this construction might be utilized in various types offurnaces in the steel industry or otherwise. Of primary significance isthe fact that furnaces of this type necessarily generate substantiallyhigh temperatures in operation; for example in the neighborhood of 2400F. V

The section 10 shown actually forms one set of skid to the pipe 17.

means or tracks extending longitudinally through a furnace (not shown)along one side thereof while a similar set or sets of tracks embodyingsubstantially identical sectional constructions might extendlongitudinally of the furnace along its opposite side and center, forexample. In this way, transversely extending billets of substantiallength are supported on each end and in the center by skid means as theyslide through the furnace while being brought up to heat.

Each section 10 of the skid means preferably includes verticallyextending insulated support pipes 11 carrying horizontally andtransversely extending insulated crossover pipes 12. The verticalsupport pipes 11 and the cross-over pipes 12 perform no other functionthan to support insulated longitudinally extending horizontal skid pipes14.

Each of the insulated furnace pipes 11, 12, and 14, includes aconventional steel pipe 17 which might be comprised of one-half inchplate. The bare pipes might be anywhere from two to eight inches indiameter. These dimensions, of course, are merely exemplary and it willbe understood that they could vary substantially within limits. Thesteel pipes 17 which form the backbone of the skid pipes 14 have wearstrips 18 secured to their upper surfaces by welding, for example. Thelongitudinally extending skid pipes 14 might be positioned on thetransversely extending cross-over pipes 14 by U-shaped brackets 19'ofany well known construction welded to the upper surface of the steelpipes 17 in the insulated crossover pipes 12.

With regard to their insulation constructions, the ver tically extendingsupport pipes 11 and the horizontal transversely extending cross-overpipes 12 are ordinarily substantially identical to each other.Consequently, only the cross-over pipes 12 will be described in detailsince the makeup of the insulation construction associated therewith iscommon to each.

Referring now to FIGURES 2 through 4, where the construction of one formof an insulated cross-over pipe 12 is shown in detail, and particularlyto FIGURE 2, the pipe 17 is shown to have a plurality of wire coils 21encircling pipe 17 at generally regularly spaced intervals therealong.These coils include a plurality of ordinary carbon steel wire coils 22and another plurality of high temperature heat resisting alloy Wirecoils 23. The high temperature heat resisting alloy is preferablystainless steel although it is conceivable that other alloys might beutilized. Consequently, the succeeding description of this inventionwill frequently refer to stainless steel wire coils, though the coilscould be formed of other metals.

It will be understood, of course, that stainless steel wire or wire of agenerally analogous composition retains its optimum physicalcharacteristics at substantially higher temperatures than ordinarycarbon steel wire. Consequently, of course, the strength of the alloysteel wire coils is retained at temperatures high enough to causeordinary carbon steel wire coils to deteriorate substantially in tensilestrength, for example, and in other physical characteristics.

It will be seen that for every stainless steel wire coil 23 encirclingthe pipe 17 there are bracketing pairs of ordinary carbon steel wirecoils 22. The significance of this relationship will be hereinafterdiscussed in detail. Threaded through each carbon steel coil 22 is acarbon steel tie wire 27 which has its opposite ends tied together, asat 28, to tightly secure corresponding individual coils 22 In turn, eachstainless steel coil 23 has a corresponding stainless steel tie wire 29threaded therethrough and tied at its ends, as at 30, for example.

33 alternating coils of stainless steel wire and carbon steel wirefrequently are desirable in crosss-over and support 1pes.

p It will also be seen that the stainless steel coils 23 have asubstantially smaller diameter than do the carbon steel coils 22. Thisrelationship is significant in certain ap* plications. and will also bediscussed hereinafter in detail. A view of the pipe 17 with itsgenerally regularly spaced coils securely tied thereon is shown inFIGURE 3. The pipe appears as such immediately precedent to applyingrefractory cement thereto.

Referring now to FIGURE 4, it will be seen that a layer 35 of refractorycement has been partially applied to the pipe 17. When applied, thisrefractory material is in a plasticized state. It might be any wellknown type of high temperature refractory material, such as Chromite,for example, as has been pointed out.

The refractory material is packed in and around the wire coils 22 and 23in its plastic state by hand or by any other well known method. Itvirtually encompasses and surrounds the generally toroidal coils andcomes into intimate contact with both the wires and the surface of thepipe 17. After a pipe is completely covered with the plasticizedrefractory material layer 35 in this manner the refractory is permittedto harden.

It is during the period when the refractory material is in its plasticstate that the ordinary carbon steel coils 22 are especiallysignificant. This is true throughout the period during which therefractory cement is hardening. The ordinary carbon steel wire coils 22have substantially large diameters and extend from the surface of thepipe 17 virtually to the surface of the refractory cement layer 35. Inthis manner, they provide completed reinforcement throughout the extentof the hardening layer 35 of refractory cement.

On the other hand, the coils of stainless steel wire 23 might besubstantially smaller in diameter in which case their outermostextremities are relatively further from the surface of the layer 35 ofrefractory cement. Although they provide a substantial amount ofreinforcement to the refractory cement in its plastic state, theirprimary purpose is to provide life long reinforcement of the hardenedrefractory material when the pipe is in operation in a high temperaturefurnace, for example.

In operative relationship, under temperatures in the neighborhood andexceeding even 2400" F., for example, the; refractory material is amplysupported and reinforced by the stainless steel wire coils 23. When theoutermost extremities of the coils 23 are somewhat removed from thesurface of the refractory layer 35, the coils are substantiallyprotected from damagingly extreme temperatures and consequently areadditionally long lived and durable reinforcements for the refractory,although the coils might, in some applications, extend substantially tothe surface of the refractory layer 35. On the other hand, the ordinarycarbon steel wire coils, their primary purpose having been served insupporting the refractory cement in its plastic state, are moresusceptible to high temperature deterioration.

The difference in diameter between the coils of stainless steel wire andordinary carbon steel wire has other ramifications also. Since asomewhat undulated surface is defined by the outermost extremities ofthe coils along the length of the pipe 17, no significant lines orplanes of weakness are set up in the hardened refractory and the dangerof cracking and consequently serious deterioration of the insulation isconsiderably lessened.

The combination wherein stainless steel coils 23 are utilized forone-half or less than one-half of the total number of coils required,and the lesser diameters of the stainless steel coils, makes theresultant insulation construction, and process for applying it,substantially less expensive than generally similar insulations andmethods heretofore utilized. In known constructions, for example, it hasbeen common practice to use unitary reinforcing means which are composedprimarily of high temperatureheat resisting alloys, due to their unitarynature, in order to insure the requisite high temperature reinforcingcharacteristics necessary to sustain reasonably long service life of theinsulated pipes. The concept embodied in this invention providesoptimium reinforcement of the refractory material in its plastic stateimmediately after application, during the hardening stages of therefractory cement, and after the insulated pipe is in service.

A considerably lesser amount of stainless steel is utilized than would,be required if all the coils were made of such material and in additioneach of the stainless steel coils is of a lesser diameter thanacorresponding ordinary carbon steel coil and consequently contains lesswire. It will readily be seen that substantial savings in the expense ofinsulated furnace pipes of this nature are realized. Nevertheless, dueto the specific utilization of the coils in this construction, aninsulationis providewhich is'superior to similar known insulations.

Another form of the insulation construction embodying features of thepresent invention, which might be utilized in the support pipes andcross-over pipes, for example, is illustrated in FIGURES 8 and 9. Again,only a crossover pipe 12 is described in detail, since the makeup of theinsulation construction inherent therein would be common to both thesupport pipes 11 and the cross-over pipes 12.

Turning now to FIGURES 8 and 9, the other form of insulationconstruction for cross-over pipes 12, referred to above, is shown indetail. Where applicable, components corresponding to components shownand described in relation to the insulation construction illustrated inFIGURES 2 through 4 will be identified by identical reference numeralsplus 100. For example, referring particularly to FIGURE 8, the pipe 117is shown to have a plurality of coils 121 encircling it at generallyregularly spaced intervals therealong. These coils include an ordinarycarbon steel wire coil 122 and another coil 123 of high temperature heatresisting alloy wire. The high temperature heat resisting alloy wire ispreferably stainless steel although it is conceivable that other alloysmight be utilized, as has been pointed out.

It will be seen that the stainless steel coil 123 encircles the pipe 117in a spiral arrangement longitudinally of the pipe. Correspondingly, theordinary carbon steel coil 122 encircles the pipe 117 in a spiralarrangement such that around any selected circumference of the pipe oralong any longitudinal line on its surface the coils 122 and 123establish an alternating sequence. Threaded through each carbon steelcoil 122 is a'carbon steel tie'wire 127 which has its opposite ends tiedto studs 131 to tightly secure the coil 122 to the pipe 117 (only oneend of the coil 122 and one stud 131 is shown, of course). In turn, eachstainless steel coil 123 has a corresponding stainless steel tie wire129 threaded therethrough and tied at its opposite ends to studs 132(only one of which is shown) welded to the surface of the pipe 117.

As pointed out, the coils 121 are arranged on the pipe 117 such that asubstantially continuous stainless steel wire coil 123 is spirally woundin parallel relationship with a carbon steel wire coil 122. This createsan alternating sequence around any chosen circumference of the pipe. Thesequence, however, is merely exemplary of the arrangements which mightbe used. In practice, for example, a single stainless steel coil 123might be spirally wound with two or more carbon steel coils 122.,

As is the case with the insulation construction illus trated in FIGURES2 through 4, it will be seen that the stainless steel coil 123 mighthave a substantially smaller diameter than does the carbon steel coil122. This relationship is-significant for the reasons hereinbcfore discussed in relation to the insulation construction shown in FIGURES 2through 4.

As seen in FIGURE 9, a layer 135 of refractory cement is applied to thepipe 117. When applied, the refractory material is in aplasticized stateand might be any well known type of high temperature material such asChromite, for example, as has also been pointed out.

In addition to the advantages inherent in the insulation constructionillustrated in FIGURES 2 through 4, the construction describedimmediately above and illustrated in FIGURES 8 and 9 has certain addedadvantages. For example, only a single operation is required inencircling the pipe with each coil of wire, since the wire coils arepreferably continuous. Consequently, labor costs are substantially lowand installation time relatively short.

Another form of the insulation construction embodying the features ofthe present invention is illustrated in FIGURE 10. Again, only across-over pipe 12 is described in detail, since the makeup of theinsulation construction inherent therein will be common both to thesupport pipes 11 and the cross-over pipes 12. Furthermore, of course, itwill be understood that the significant aspects of thepresent inventionare readily adaptable to use with skid pipes.

Returning now to FIGURE 10, once more, where applicable, componentscorresponding to components shown and described in relation to theinsulation construction illustrated in FIGURES 8 and 9 will beidentified by identical reference numerals plus 100. For example,referring particularly to FIGURE 10, the pipe 217 is shown to have aplurality of coils 221 encircling it at generally regularly spacedintervals therealong. These coils include an ordinary carbon steel wirecoil 222 and another coil 223 of high temperature heat resisting alloywire which is preferably stainless steel although it is conceivable thatother alloys might be utilized, as has been pointed out.

It will be seen that the stainless steel coil 223 encircles the pipe 217in a spiral arrangement longitudinally of the pipe. correspondingly, theordinary carbon steel coil 222 encircles the pipe 217 in a spiralarrangement such that around any selected circumference of the pipe oralong any longitudinal line on its surface the coils 222 and 223establish an alternating sequence. Threaded through each carbon steel'coil 222 is a carbon steel tie wire 227 which has its opposite endstied to studs (not shown) to tightly secure the coil 222 to the pipe217. In turn, each stainless steel coil 223 has a correspondingstainless steel tie wire 229 threaded therethrough and tied at itsopposite ends to studs (not shown) welded to the surface of the pipe217.

As pointed out, the coils 221 are arranged on the pipes 217 such that asubstantially continuous stainless steel wire coil 223 is spirally woundin parallel relationship with a carbon steel wire coil 222. This createsan alternating sequence around any chosen circumference of the pipe oralong any longitudinal line on its surface. The sequence, however, ismerely exemplary of the arrangements which might be used. In practice,for example, a single stainless steel wire coil 223 might be spirallywound with two or more carbon steel Wire coils 222.

In the insulation arrangement shown in FIGURE 10, however, it will beseen that the stainless steel coils 223 are substantially of the samediameter as the carbon steel coils 222.v The outermost extremities ofboth coils, then, extend substantially to the surface of the refractory235. Unlike methods of insulation using a metal reinforcement such as areticulated wire structure where it has been considered necessary tocover the entire structure with a substantial thickness of refractorymaterial 'in order to protect the metal structure from the furnace heatwhich would seriously Weaken or destroy the structure, the presentinventions utilization of wire coils with tie wires threaded throughthem obviates this necessity g the utilization of separate wire coils inthe manner of the construction shown in FIGURES 1 through 7, forexample, as it does to a spiral construction.

Departing the construction of the various forms of vertical supportpipes 11 and cross-over pipes 12, and referring now to FIGURES 5 through7, the insulation construction and method of insulating skid pipes 14 isshown in detail. In essence, since a wear strip 18 is welded to theupper surface of the steel pipe 17 forming the backbone of skid pipe 14,to provide a sliding surface for the billets of steel being supported bythe skid pipes, the coils of stainless steel wire are anchored to thepipe on opposite sides of the wear strip 18 while the ordinary carbonsteel coils are tied in the manner hereinbefore 0 described inencircling relationship of both the pipe and the wear strip.

Referring specifically to FIGURE 5, it will be seen that studs 40 havingcollars 41 thereon are welded to the surface of the steel pipe 17 atgenerally regularly spaced intervals in longitudinal alignment alongopposite sides of the wear strip 18. The studs 40 provide means foranchoring the opposite ends of the stainless steel tie wires 29extending through the coils 23 of stainless steel wire. The tie wires 29might be secured to the studs by being wrapped therearound and reversedto be wrapped around themselves, as seen in FIGURE 6. The use of studsis merely exemplary, however, and other means of anchoring the ends ofthe stainless steel wire might be utilized.

On the other hand, the coils 22 of ordinary carbon steel wire aresecured to the pipe 17 without the benefit of anchoring studs. The tiewires 27 are threaded through corresponding coils 22 of carbon steelwire and tied over the wear strip 18, as at 45. The free ends 46 of thetie wires 27 securing the carbon steel coils 22 to the pipe 17 might betied, as at 50, to one or more of the adjoining studs 40.

As seen in FIGURE 7, the layer 35 of refractory cement in its plasticstate is applied to the surface of the pipe 17 such that it encompassesand surrounds the wire coils 22 and 23 and the studs 40. In thisrelationship it is in intimate contact with the surface of the pipe 7-17, each of the wire coils'22 and 23 and the tie wires 27 and 29, andhardens in this relationship. During the hardening process, therefractory material is supported to a great extent by the largerdiameter carbon steel coils 22. Considerable support is also offered, aswill easily be understood, by the alloy steel coils 23 which are ofsomewhat smaller diameter and consequently do not extend as close to thesurface of the layer 35 of refractory cement as do the carbon steelcoils 22.

After the refractory cement is hardened, the tie wires 27 for theordinary carbon steel coils 22 might be snipped on opposite sides of thewear strip 18, as at 51, where they protrude from the refractorymaterial, and the pipe is ready for service. In practice, however, theprotruding wires are ordinarily left intact for the heat of the furnaceto soften and oxidize wherein they are sheared or broken by steel beingpushed onto the skids. At intervals along the length of the skid pipes14, the steel pipe 17 forming the backbone of the skid pipes might beleft bare of insulation to afford a spot for con-tact by the brackets 19in supporting relationship. However, this feature forms no part of theinvention and it is not thought necessary that it be shown in detail.

Of course, the primary advantages inherent in the insulationconstruction of the skid pipes 14 are similar to those inherent in theinsulation construction of the various forms of cross-over pipes 12hereinbefore described. For example, since the coils are of somewhatvarying diameter, no planes or lines of weakness are es 'tablished inthe hardened insulation and consequently the durability and life of theinsulation is greatly improved.

In the insulation construction utilized for both the cross-over andsupport pipes and the skid pipes, there are substantial advantages notfound in the insulation constructions or methods for insulating hightemperature water cooled furnace pipes utilized ,in the industry today.As has been pointed out, a substantial saving in cost is realized byvirtue of the fact that the amount of high temperature heat resistingalloy wire required to secure durable insulation is considerably lessthan in known similar arrangements.

The specific arrangement of the alternating or otherwise interspersedcoils of varying diameter carbon steel and stainless steel wire is suchthat the stainless steel coils can be better protected from the maximumtemperatures generated in the furnace. In such case, as has been pointedout, the outermost extremities of the alternating coils define asomewhat undulating surface which does not set up lines or planes ofweakness in the hardened refractory. The insulation construction whichresults is less expensive, more durable,- and easier to construct thansimilar known arrangements.

Moreover, when an insulation construction embodies only certain aspectsof the present invention, as illustrated in FIGURE 10, for example,satisfactory anchorage is also provided for the refractory material; Thetie wires hold the coils or remaining portions of the coils even if theyare partially burned and merely become hooks embedded in the refractory.A- mere burning away of a portion of, the coil does not substantiallylessen the strength of the reinforcement because the tie Wire retainsthe remaining portions of the coil which is embedded in the refractoryand keeps it from falling off the pipe even if the refractory developscracks. This is a great advantage of using the present coil and tie wireconstruction over certain forms of reticulated metal structure which aremore or less dependent upon retaining continuity of the entire structurein order to retain their strength.

Although the coils 22, 23, etc., have been described herein solely asencircling the pipes 17, etc., it should be understood that they extendcireumferentially of their respective pipes in doing so. This is true ineach embodi ment of the invention described.

While several embodiments described herein are at present considered tobe preferred, it is understood that various modifications andimprovements may be made therein, and it is intended to cover in theappended claims all such modifications and improvements as fall withinthe true spirit and scope of the invention.

What is desired to be claimed and secured by Letters Patent of theUnited States is:

l. A reinforced insulating covering for a furnace pipe comprisinginsulation means, said insulation means in cluding coil means fabricatedof substantially high temperature heat resisting wire adapted to extendcircumferentially of the pipe, said coil means including a series ofcircumferentially extending coil portions separated from each otheralong any longitudinal line through said insulation means, the wire ofeach of said coil portions in itself coiling about an axis adapted toencircle the pipe, means adapted to secure said coil means to the pipe,said insulation means further including a layer of refractory materialencompassing and intimately contacting the wire of said coil means andadapted to intimately contact and surround the pipe.

2. An insulated pipe construction comprising a pipe, coil meansextending circumferentially of said pipe and fabricated of substantiallyhigh temperature heat resisting wire, said coil means including a seriesof circumferentially extending coil portions separated from each otheralong any longitudinal line on said pipe, the wire of each of said coilportions in itself coiling about an axis encircling said pipe, meanssecuring said coil means to said pipe, and a layer of refractorymaterial surrounding said pipe and intimately contacting said pipe andthe wire of said coil means.

3. The insulation of claim 1 further characterized in that said coilmeans of substantially high temperature heat resisting wire comprises asubstantially continuous coil of wire extending ingenerally spiralrelationship longitudinally in said insulation.

4. A reinforced insulationfor afurnace pipe comprising a coil ofsubstantially high temperature heat resisting wire adapted to extendcircumferentially of the pipe, means adapted to secure saidsubstantially. high temperature heat resisting wire coil to the pipe, acoil of relatively lower temperature heat resisting wire spaced-fromsaid substantially high temperature heat resisting wire coil and adaptedto extend circumferentially of the pipe, means adapted to secure saidrelatively low temperature heat resisting wire coil to the pipe, and alayer of refractory material-intimately contacting andsurrounding thewire of said coils and adapted to intimately contact and surround thepipe.

5. The insulation of claim 4- further characterized in that said coilsextend substantially. parallel to each other in generally spiralrelationship longitudinally in said insulation. i

6. The insulation of claim 4 further characterized in that eachof saidsecuring means includes tie wire means extending through said coils.

7. The insulation of claim 5 further characterized in that each of saidsecuring means includes tie wire means extending through said coils.

8. The insulation of claim 4' further characterized in that said coil ofsubstantially high temperature heat resisting wire is of a smallerdiameter than said coil of relatively low temperature heat resistingwire.

9. The insulation of claim 5 further characterized in that said coilofsubstantially high temperature heat resisting wire is of a smallerdiameter than said coil of relatively low temperature heat resistingwire.

10. An insulated pipe construction comprising a pipe, a coil ofsubstantially high temperature heat resisting wire extendingcircumferentiaily of said pipe, means securing said substantially hightemperature heat resisting Wire coil to said pipe, a coil of relatively.low temperature heat resisting Wire spaced from said substantially hightemperature heat resisting Wire coil and extending, circumferentially ofsaid pipe, means securing said relatively low temperature heat resistingwire coil to said pipe, and a layer of refractory material surroundingsaid pipe and intimately contacting said pipe and the wire of saidcoils.

11. The insulated pipe construction of claim 10 further characterized inthat said coils of wire extend substantially parallel to each other ingenerally spiral relationship longitudinally of said pipe.

12. An insulated pipe construction comprising a pipe, a plurality ofcoils of substantially high temperature heat resisting wire extendingcircumferentially of said pipe, a substantially high temperature heatresisting tie wire extending through each of said coils, means anchoringthe opposite ends of said substantially high temperature heat resistingtie wires to secure said substantially high tem perature heat resistingwire coils to said pipe, a plurality of relatively low temperature heatresisting wire coils interspersed and spaced from said substantiallyhigh temperature heat resisting wire coils and extendingcircumferentially of said pipe, a relatively low temperature heatresisting tie wire extending through each of said relatively lowtemperature heat resisting wire coils, means anchoring the opposite endsof said relatively low temperature heat resisting tie wires to securesaid relatively low temperature heat resisting wire coils to said pipe,and a layer of refractory material surrounding said pipe and intimatelycontacting said pipe and the Wire of said coils.

13. The insulated furnace pipe construct-ion of claim 12 furthercharacterized in that the diameter of said substantially hightemperature heat resisting wire coils is less than the diameter of saidrelatively low temperature heat resisting wire coils.

14. An insulated furnace pipe construction comprising amass? i i a pipe,a coil of substantially high temperature heat resisting wire extendingcircumferentially of said pipe, a substantially high temperature heatresisting tie wire extending through said substantially high temperatureheat resisting wire coil and securing said coil to said pipe, arelatively low temperature heat resisting wire coil spaced from saidsubstantially high temperature heat resisting wire coil and extendinggenerally parallel thereto circumferentially of said pipe, a relativelylow temperature heat resisting wire extending through said relativelylow temperature heat resisting wire coil and securing said relativelylow temperature heat resisting wire coil to said pipe, and a layer ofrefractory material surrounding said pipe and intimately contacting saidpipe and the wire of said coils.

15. The insulated furnace pipe construction of claim 14 furthercharacterized in that the diameter of said relatively low temperatureheat resisting wire coil is slightly greater than the diameter of saidsubstantially high temperature heat resisting wire coil, the thicknessof said layer of refractory material being slightly greater than thediameter of said relatively lowtemperature heat resisting Wire coil.

16. The insulated furnace pipe construction of claim 15 furthercharacterized in that said coils of wire are disposed in a spiralarrangement circumferentially and longitudinally of said pipe.

17. The insulation construction of claim 15 further characterized inthat said substantially high temperature heat resisting wire coil isstainless steel.

18. An insulated water coiled skid pipe construction comprising a pipe,longitudinally extending skid means secured to said pipe, a plurality ofcoils of substantially high temperature heat resisting wire extendingcircumferentially of said pipe, a substantially high temperature heatresisting tie Wire extending through each of said coils, V

stud means extending from said pipe on opposite sides of said skidmeans, the opposite ends of said substantially high temperature heatresisting tie wires being secured to corresponding stud means to securesaid substantially high temperature heat resisting wire coils to saidpipe, a plurality of relatively low temperature heat resisting wirecoils interspersed with and spaced from said substantially hightemperature heat resisting wire coils and extending circumferentially ofsaid pipe, a relatively low temperature heat resisting tie wireextending through each of said ture heat resisting wire coils aresubstantially toroidal in configuration, the diameter of saidsubstantially high temperature heat resisting wire coils being somewhatless than the diameter of said relatively low temperature heat resistingwire coils.

20. A method of insulating a pipe for use in high temperature furnacescomprising the steps of encircling the pipe with a coil oi substantiallyhigh temperature heat resisting wire, securing the coil of substantiallyheat resisting wire to the pipe with a tie wire passing therethrough,encircling the pipe with a coil of relatively low temperature heatresisting wire extending substantially parallel to said coil ofsubstantially high temperature heat resisting wire, securing said coilof relatively low temperature heat resisting wire to said pipe with atie wire passing therethrough, and covering the pipe and coils with alayer of plasticized refractory material such that the refractorymaterial encompasses and surrounds the wire coils and comes intointimate contact with the surface of the pipe and the wire, and allowingthe refractory material to harden in this relationship.

21. The method of claim 20 further characterized in that said coil ofsubstantially high temperature heat resisting wire has a lesser diameterthan said coil of relatively low temperature heat resisting Wire.

22. The method of claim 21 further characterized in that said pipe isencircled with a plurality of substantially high temperature heatresisting wire coils and a plurality of relatively low temperature heatresisting wire coils in sequential relationship, spaced longitudinallyof said pipe.

Stanbery et al Apr. 8, 1930 Bloom Nov. 2, 1954 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No. 3, 168 ,297 February 2 1965John R. Brough It is hereby certified that error appears in the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below Column 1, line 61, for "ski" read skidcolumn 3, line 14, for "realtionship" read relationship line 26, for"plane" read planes column 6, line 18, for "provide" read providedcolumn 11, line 31, for "coiled" read cooled Signed and sealed this 29thday of June 1965.

(SEAL) Attest:

ERNEST w. SWIDER EDWARD J. BRENNER Aitesting Officer Commissioner ofPatents

1. A REINFORCED INSULATING COVERING FOR A FURNACE PIPE COMPRISINGINSULATION MEANS, SAID INSULATION MEANS INCLUDING COIL MEANS FABRICATEDOF SUBSTANTIALLY HIGH TEMPERATURE HEAT RESISTING WIRE ADAPTED TO EXTENDCIRCUMFERENTIALLY OF THE PIPE, SAID COIL MEANS INCLUDING A SERIES OFCIRCUMFERENTIALLY EXTENDING COIL PORTIONS SEPARATED FROM EACH OTHERALONG ANY LONGITUDINAL LINE THROUGH SAID INSULATING MEANS, THE WIRE OFEACH OF SAID COIL PORTIONS IN ITSELF COILING ABOUT AN AXIS ADAPTED TOENCIRCLE THE PIPE, MEANS ADAPTED TO SECURE SAID COILS MEANS TO THE PIPE,SAID INSUALTION MEANS FURTHER INCLUDING A LAYER OF REFRACTORY MATERIALENCOMPASSING AND INTIMATELY CONTACTING THE WIRE OF SAID COIL MEANS ANDADAPTED TO INTIMATELY CONTACT AND SURROUND THE PIPE.